Physical stress on a silver halide emulsion capable of deforming the silver halide grains or disrupting the silver halide-gelatin surface generally correlates to a negative photographic effect. Such stress may result in an increase in emulsion density, i.e., fog, or desensitization, or the destruction of already existing latent image. Silver halide emulsions are soft materials, with less hardness than dry gelatin, so that excessive sharp bending of a film, or excessive local stretching, causes marks in the area involved. In general, the effect of stress after exposure of the photosensitive material is less than those produced upon an unexposed emulsion. If the film is sharply bent, a usual result is an appearance of fog or an increase in density along the line of bending and desensitization. Typical cases of pressure marks occur when film is kinked, when a large sheet is handled and when film is pulled under tension around a small roller, especially if the motion is intermittent; or when film is stretched near sprocket holes.
Photosensitive materials are likely to be pulled under tension or stretched by rollers while in a processing apparatus while undergoing development with a developer solution of a latent image to a visible image. In particular, the detrimental effects of tension and stretching on the photosensitive material manifest themselves as pressure marks when the photosensitive material is transported through the development section of a processing apparatus. These pressure marks which occur while in the development section of a processor are usually called "wet pressures". Sensitivity resulting in wet pressure marks may be affected to a different degree or even in opposite directions by different types of photosensitive materials, i.e., x-ray, medical, graphics arts, etc.
Thus far, prior methods for determining the sensitivity of a photosensitive material to wet pressure induced marks have not been reproducible and have been cumbersome and time consuming. Prior to the discovery of this invention, pressure in photosensitive material film was introduced by disassembling a roller of a processing apparatus, wrapping a tape around the roller and then reassembling the roller in a processor. This method was generally not successful since the tape tended to unwrap and loosen on the roller due to the wet chemistry. Also, the results were highly dependent upon operator technique.
It is therefore an object of this invention to provide a quick and easy-to-accomplish method for determining the wet pressure sensitivity of silver halide photosensitive materials.